JP5987651B2 - Zoom lens, camera, and portable information terminal device - Google Patents

Description

  The present invention relates to a zoom lens, a camera, and a portable information terminal device.

  In recent years, an increasing number of users desire higher image quality and downsizing of cameras and digital cameras. In addition, there are an increasing number of users who wish to widen the angle of the taking lens. These user needs are also required when a zoom lens is used as a photographing lens.

  In general, in order to increase the angle of the zoom lens, it is desirable that the half angle of view at the short focal point of the zoom lens is about 45 degrees. However, in order to make the zoom lens have a wide angle, the size of the zoom lens in the radial direction must be increased. Therefore, there is a contradiction between the wide angle and the miniaturization of the zoom lens.

  In addition, in order to improve the image quality of a camera or the like, it is necessary to have a resolution corresponding to an image sensor with at least 10 million to 15 million pixels in all zoom ranges. Further, it is desired to increase the diameter of the zoom lens, and it is desirable that the F number at the short focal end can be set to 2.0 or less and the F number at the long focal end can be set to about 3.0.

  There are many types of zoom lenses for digital cameras. Among them, as a zoom lens suitable for increasing the diameter, the first lens group moves so as to be convex toward the image side, the second lens group moves toward the image side, and the third lens group moves toward the object side. A zoom lens in which the fourth lens group moves is known. Such a zoom lens has, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. A fourth lens group. The third lens group includes a positive lens L31, a positive lens L32, a negative lens L33, a negative lens L34, a positive lens L35, and a positive lens L36 in order from the object side (for example, Patent Document 1, Patent Document 2, Patent Document 3, See).

  The zoom lenses described in Patent Documents 1 to 3 are suitable for increasing the aperture, but in order to achieve both a wide angle and a small size, the half angle of view is set to about 45 degrees and the F number with a short focal length is short. Is not more than 2.0 and the F number at the long focal end is about 3.0, and further miniaturization cannot be achieved.

  The present invention has been made in view of the above problems, and the half angle of view at the short focus end is sufficiently wide as about 45 degrees, the F number at the short focus end is 2.0 or less, and the long focus angle. An object of the present invention is to provide a small zoom lens while the F number at the end is about 3.0.

  In the present invention, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a positive refractive power. A lens group, and during zooming from the short focal end to the long focal end, the distance between the first lens group and the second lens group is increased, and the distance between the second lens group and the third lens group is decreased, In the zoom lens in which the distance between the third lens group and the fourth lens group is changed, an aperture stop is disposed between the second lens group and the third lens group, and the third lens group sequentially includes a positive lens L31, It has a positive lens L32, a negative lens L33, a negative lens L34, a positive lens L35, and a positive lens L36. The fourth lens group is composed of one or two lenses, and focusing is performed by the fourth lens group. On the axis of the third lens group and the fourth lens group at the long focal end And septum D34_T, the focal length f4 of the fourth lens group, the condition (1): 0.2 <a main satisfies the D34_T / f4 <0.5.

  According to the present invention, the half angle of view at the short focus end is sufficiently wide as about 45 degrees, the F number at the short focus end is 2.0 or less, and the F number at the long focus end is about 3.0. Nevertheless, a small zoom lens can be provided.

FIG. 2 is an optical arrangement diagram showing a short focal end (a), an intermediate focal length (b), and a long focal end (c) according to Example 1, which is an embodiment of a zoom lens according to the present invention. FIG. 4A is a diagram of (a) spherical aberration, (b) astigmatism, (c) distortion, and (d) coma at the short focal point according to Example 1 of the zoom lens. FIG. 4A is a spherical aberration diagram, FIG. 5B is an astigmatism diagram, FIG. 5C is a distortion diagram, and FIG. FIG. 5A is a (a) spherical aberration diagram, (b) an astigmatism diagram, (c) a distortion diagram, and (d) a coma aberration diagram at the long focal point according to Example 1 of the zoom lens. FIG. 5 is an optical arrangement diagram showing a short focal end (a), an intermediate focal length (b), and a long focal end (c) according to Example 2, which is an embodiment of a zoom lens according to the present invention. (A) Spherical aberration diagram, (b) Astigmatism diagram, (c) Distortion diagram, and (d) Coma diagram of the short focal point according to Example 2 of the zoom lens. (A) Spherical aberration diagram, (b) Astigmatism diagram, (c) Distortion diagram, (d) Coma diagram of intermediate focal length according to Example 2 of the zoom lens. (A) Spherical aberration diagram, (b) Astigmatism diagram, (c) Distortion diagram, and (d) Coma aberration diagram of the long focal point according to Example 2 of the zoom lens. FIG. 5 is an optical arrangement diagram showing a short focal end (a), an intermediate focal length (b), and a long focal end (c) according to Example 3, which is an embodiment of a zoom lens according to the present invention. (A) Spherical aberration diagram, (b) Astigmatism diagram, (c) Distortion diagram, and (d) Coma diagram of the short focal point according to Example 3 of the zoom lens. (A) Spherical aberration diagram, (b) Astigmatism diagram, (c) Distortion diagram, (d) Coma diagram of intermediate focal length according to Example 3 of the zoom lens. (A) Spherical aberration diagram, (b) Astigmatism diagram, (c) Distortion diagram, and (d) Coma aberration diagram of the long focal point according to Example 3 of the zoom lens. FIG. 6 is an optical arrangement diagram illustrating a short focal end (a), an intermediate focal length (b), and a long focal end (c) according to an embodiment 4 of a zoom lens according to the present invention. (A) Spherical aberration diagram, (b) Astigmatism diagram, (c) Distortion diagram, and (d) Coma diagram of the short focal point according to Example 4 of the zoom lens. (A) Spherical aberration diagram, (b) Astigmatism diagram, (c) Distortion diagram, (d) Coma diagram of intermediate focal length according to Example 4 of the zoom lens. (A) Spherical aberration diagram, (b) Astigmatism diagram, (c) Distortion diagram, and (d) Coma diagram at the long focal point according to Example 4 of the zoom lens. FIG. 6 is a diagram for explaining electronic correction of distortion in the zoom lens according to Example 2 described above. FIG. 2A is an external perspective view of the object side, and FIG. 3B is an external perspective view of the back side, showing an embodiment of a camera using the zoom lens in a photographing optical system. It is a block diagram which shows the example of a function structure of the camera which used the said zoom lens for the imaging | photography optical system.

  Hereinafter, embodiments of a zoom lens, a camera, and a portable information terminal according to the present invention will be described with reference to the drawings.

  First, an embodiment of a zoom lens according to the present invention will be described. The zoom lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a positive refractive power. A fourth lens unit having When zooming from the short focal end to the long focal end, the zoom lens increases the distance between the first lens group and the second lens group, and decreases the distance between the second lens group and the third lens group. In this zoom lens, the distance between the third lens group and the fourth lens group changes. This zoom lens has the characteristics shown in the following embodiments.

A zoom lens according to an embodiment of the present invention has the following configuration. That is, the third lens group in order from the object side is a positive lens (referred to as a lens having positive refractive power; hereinafter the same) L31, a positive lens L32, and a negative lens (referred to as a lens having negative refractive power; hereinafter the same). .) L33, a negative lens L34, a positive lens L35, and a positive lens L36. The fourth lens group is composed of one or two lenses, and focusing is performed by the fourth lens group. Then, “D34_T” that is the axial distance between the third lens group and the fourth lens group at the long focal end and “f4” that is the focal length of the fourth lens group satisfy the following conditional expression 1. .
(Condition 1)
0.2 <D34_T / f4 <0.5

  Like the zoom lens described above, the zoom lens including four lens groups having “positive, negative, positive, positive” refractive powers from the object side is configured as a so-called variator in which the third lens group bears a main zooming action. Is done.

  Upon zooming from the short focal end to the long focal end, the first lens unit moves so as to be convex toward the image side, the second lens unit moves toward the image side, and the third lens unit moves toward the object side. The fourth lens group moves. As a result, the distance between the first lens group and the second lens group is increased, the distance between the second lens group and the third lens group is decreased, and the magnification (absolute value) of the second lens group and the third lens group is Both increase, but the magnification is mainly changed by the third lens group.

  Furthermore, since the light flux passing through the third lens group may become thick, the configuration of the third lens group becomes important in order to reduce the F number and achieve high performance. Therefore, the configuration of the third lens group is a positive lens L31, a positive lens L32, a negative lens L33, a negative lens L34, a positive lens L35, and a positive lens L36.

  By arranging this third lens group symmetrically in the form of “positive lens L31, positive lens L32, negative lens L33” and “negative lens L34, positive lens L35, positive lens L36”, various aberrations are sufficiently obtained. Can be corrected. Further, it is preferable that the positive lens L32 and the negative lens L33 are cemented and the negative lens L34 and the positive lens L35 are cemented. Furthermore, in order to perform focusing up to a short distance at the long focal end while having high performance, the above-described conditional expression 1 may be satisfied.

  According to the zoom lens described above, the half angle of view at the short focus end is 42 degrees or more, the F number at the short focus end is 2.0 or less, and the F number at the long focus end is about 3.0. The number of sheets is about 11. Accordingly, it is possible to provide a zoom lens having a resolving power corresponding to a small image sensor with 10 to 20 million pixels.

  If the upper limit value shown in the conditional expression 1 is exceeded, the distance between the third lens group and the fourth lens group becomes too wide at the long focal end, and the total lens length becomes too large, or the power of the fourth lens group is too strong. Thus, the aberration generated in the fourth lens group becomes too large. As a result, it becomes difficult to correct aberrations in the entire zoom range.

  If the lower limit value shown in the conditional expression 1 is exceeded, focusing to a short distance at the long focal end becomes impossible.

In the zoom lens described above, “D34_W” that is the axial distance between the third lens group and the fourth lens group at the short focal point and “f4” that is the focal length of the fourth lens group are the following conditional expressions: It is desirable to satisfy 2.
(Condition 2)
0.05 <D34_W / f4 <0.15

  By satisfying Conditional Expression 2 above, it is possible to perform focusing up to a short distance at the short focal end with high performance. Accordingly, it is possible to provide a zoom lens that can correct each aberration well and can focus to a short distance at the short focal end.

  If the upper limit value shown in conditional expression 2 is exceeded, the distance between the third lens group and the fourth lens group becomes too wide at the long focal end and the total lens length becomes too large, or the power of the fourth lens group is too strong. Thus, the aberration generated in the fourth lens group becomes too large. As a result, it becomes difficult to correct aberrations in the entire zoom range.

  If the lower limit value shown in conditional expression 2 is exceeded, focusing to a short distance at the short focal end becomes impossible.

In the zoom lens described above, it is preferable that “f4”, which is the focal length of the fourth lens group, and “fw”, which is the focal length of the short focal end, satisfy the following conditional expression 3.
(Condition 3)
5 <f4 / fw <8

  By satisfying the above conditional expression 3, a further high-performance zoom lens can be obtained. As a result, it is possible to provide a high-performance zoom lens in which each aberration is corrected more satisfactorily.

  If the upper limit value shown in the conditional expression 3 is exceeded, the exit pupil becomes too close to the image plane and the telecentricity deteriorates.

  If the lower limit value shown in conditional expression 3 is exceeded, it will be difficult to correct the aberration generated in the fourth lens group with a simple configuration. Therefore, it is desirable that the fourth lens group is composed of one lens.

In the zoom lens described above, “D3” that is the thickness of the third lens group on the optical axis and “fw” that is the focal length of the short focal point satisfy the following conditional expression 4. Is desirable.
(Condition 4)
2 <D3 / fw <3

  By satisfying Conditional Expression 4 above, it is possible to obtain a high-performance zoom lens that is small in size.

  If the upper limit value shown in the conditional expression 4 is exceeded, the distance between the second lens group and the third lens group and the thickness of the second lens group on the optical axis are reduced by the thickness of the third lens group. This makes it difficult to correct aberrations in the entire zoom range.

  If the lower limit value shown in conditional expression 4 is exceeded, the thickness of the third lens group becomes too thin, and it becomes difficult to correct various aberrations in the third lens group.

In the zoom lens described above, it is preferable that “f3”, which is the focal length of the third lens group, and “fw”, which is the focal length of the short focal end, satisfy the following conditional expression 5.
(Condition 5)
2.5 <f3 / fw <3.5

  By satisfying the above conditional expression 5, it is possible to obtain a higher performance zoom lens in which each aberration is corrected more satisfactorily.

  If the upper limit value shown in conditional expression 5 is exceeded, it will be difficult to perform zooming with the third lens group, and it will be difficult to correct aberrations in the entire zoom range.

  If the lower limit value shown in the conditional expression 5 is exceeded, the focal length of the third lens group becomes too short, and it becomes difficult to correct various aberrations in the third lens group.

It is desirable that the zoom lens described above further satisfies the following conditional expression 6. Here, “Da” is the distance on the optical axis from the object side surface of the positive lens L31 to the image side surface of the negative lens L33. “D3” is the thickness of the third lens group on the optical axis.
(Condition 6)
0.4 <Da / D3 <0.6

  By satisfying the conditional expression 6 described above, the monochromatic aberration and the chromatic aberration are exchanged between the object side surface of the positive lens L31 and the image side surface of the negative lens L33 so that the aberration can be corrected as a whole. As a result, a high-performance zoom lens in which each aberration is corrected more satisfactorily can be obtained.

  In the zoom lens described above, it is further desirable that the diaphragm moves independently during zooming from the short focal end to the long focal end. According to this zoom lens, since the stop is located on the object side at the short focal end, the group closer to the object side than the stop can be made smaller, and the group located closer to the object side than the stop can be corrected with a simple configuration. be able to. Thereby, a small and high-performance zoom lens can be provided.

The zoom lens described above preferably further satisfies the following conditional expression 7. Here, “TL3s_w” is the distance between the stop and the third lens group at the short focal end. “TL2s_w” is the distance between the second lens group and the stop at the short focal end.
(Condition 7)
0.15 <TLs3_w / TL2s_w <0.40

  By satisfying the above conditional expression 7, it is possible to obtain a further compact and high-performance zoom lens.

  If the lower limit value of conditional expression 7 is exceeded, the distance between the second lens group and the stop becomes large, the off-axis ray passing through the second lens group at the short focal end becomes too high, and the off-axis within the second lens group. Aberration correction becomes difficult, and the second lens group becomes large.

  When the upper limit value of conditional expression 7 is exceeded, the distance between the third lens group and the stop becomes large, the off-axis rays passing through the third lens group at the short focal end become too high, and aberration correction in the third lens group is performed. And the third lens group becomes large.

  Further, in the zoom lens described above, it is desirable that each lens group individually moves when zooming from the short focal end to the long focal end. That is, the first lens group moves so as to be convex toward the image side, the second lens group moves toward the image side, the third lens group moves toward the object side, and the fourth lens group moves toward the object side. It is desirable to change the magnification so that the distance between the fifth lens group and the fourth lens group is increased.

  When it is necessary to reduce the amount of light reaching the image plane, the diameter of the diaphragm may be reduced. However, if the amount of light is reduced by inserting an ND filter or the like without greatly changing the diameter of the diaphragm, the resolving power due to the diffraction phenomenon is reduced. It is preferable because it can prevent a decrease.

  Next, an embodiment of a camera according to the present invention will be described. The camera according to the present embodiment includes the zoom lens described above in the photographing optical system. As a result, the half angle of view at the wide-angle end is a sufficiently wide angle of 42 degrees or more, but the F number at the short focal end is 2.0 or less and the F number at the long focal end is about 3.0. In addition, a camera including a zoom lens having high resolving power can be realized.

  Next, an embodiment of a portable information terminal device according to the present invention will be described. The portable information terminal device according to the present embodiment includes the above-described zoom lens in the photographing optical system of the camera function unit. As a result, the half angle of view at the wide-angle end is a sufficiently wide angle of 42 degrees or more, but the F number at the short focal end is 2.0 or less and the F number at the long focal end is about 3.0. In addition, it is possible to realize a portable information terminal device including a zoom lens having a high resolving power in a camera function unit.

  Next, specific examples of the zoom lens according to the present invention will be described with numerical values. The zoom lenses according to Examples 1 to 4 described below have a positive, negative, positive positive four-group configuration. In each embodiment, the parallel plate disposed on the image plane side of the fourth lens group is made of various filters such as an optical low-pass filter and an infrared cut filter, and a cover glass (seal glass) of a light receiving element such as a CMOS sensor. It is assumed.

  The zoom lens according to each example indicates that the aberration is sufficiently corrected, and indicates that the zoom lens according to the present invention is compatible with a light receiving element with 10 to 20 million pixels. In addition, it is shown that the zoom lens according to each embodiment can ensure a very good image performance while achieving a sufficient size reduction.

Symbols in each example are as follows.
f: Focal length of entire system F: F number ω: Half angle of view R: Radius of curvature D: Surface spacing Nd: Refractive index νd: Abbe number φ: Ray effective length K: Aspherical conic constant A ₄ : 4th order Aspheric coefficient A ₆ : 6th-order aspheric coefficient A ₈ : 8th-order aspheric coefficient A ₁₀ : 10th-order aspheric coefficient For an aspheric surface, the reciprocal of the paraxial radius of curvature (paraxial curvature) is C When the height from the optical axis is H, it is defined by the following equation.
^{X = CH 2 / [1+ {} 1- (1 + k) C 2 H 2} 1/2] + A 4 H 4 + A 6 H 6 + A 8 H 8 + A 10 H 10

  In the “Glass” column in the table showing numerical examples in each example, the manufacturer and the optical glass type name are described. In the description in the column, (OHARA) is an abbreviation for “Ohara Inc.”, and (HIKARI) is an abbreviation for “Hikari Glass Co., Ltd.”.

  1A and 1B show an optical arrangement of a zoom lens according to Example 1. FIG. 1A shows a lens group arrangement at the wide-angle end (short focal end), and FIG. 1B shows a lens group arrangement at an intermediate focal length. (C) shows the lens group arrangement at the telephoto end (long focal end). As shown in FIG. 1, when zooming from the wide-angle end to the telephoto end, each lens group of the zoom lens moves as indicated by an arrow.

  The zoom lens shown in FIG. 1 includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power in order from the object side to the image plane side along the optical axis. And a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power.

The aperture stop S is disposed between the second lens group G2 and the third lens group G3. The symbol F indicates “transparent parallel plate”. The transparent parallel plate F exemplifies various filters such as an optical low-pass filter and an infrared cut filter (transparent parallel plate on the object side) and a cover glass (transparent parallel plate on the seal glass image side) of an image sensor such as a CCD sensor. It is.

  The first lens group G1 includes a single first lens L11.

  The second lens group G2 includes a first lens L21, a second lens L22, and a third lens L23. The first lens L21 of the second lens group G2 is a hybrid aspherical lens that becomes an aspherical lens by a resin film provided on the object side surface.

  The third lens group G3 includes a first lens L31, a second lens L32, a third lens L33, a fourth lens L34, a fifth lens L35, and a sixth lens L36.

  The fourth lens group G4 includes a single first lens L41.

  The first lens group G1 to the fourth lens group G4 are each supported by a common support frame or the like appropriate for each lens group, and operate relatively for each lens group during zooming or the like. The aperture stop S moves independently of each lens group upon zooming from the short focal end to the long focal end.

  In the zoom lens according to Example 1, all the groups of the first lens group G1 to the fourth lens group G4 move during zooming from the wide-angle end (short focal end) to the telephoto end (long focal end). The first lens group G1 moves so as to be convex toward the image plane side, the second lens group G2 moves toward the image plane side, the third lens group G3 moves toward the object side, and the fourth lens group G4 moves. To do. By the movement of each lens group, the distance between the first lens group G1 and the second lens group G2 is increased, and the distance between the second lens group G2 and the third lens group G3 is decreased.

  2 to 4 are aberration diagrams of the zoom lens according to Example 1. FIG. 2 is an aberration curve diagram at the short focal end, FIG. 3 is an aberration curve diagram at the intermediate focal length, FIG. 4 is an aberration curve diagram at the long focal end, and (a) in each figure shows spherical aberration, ) Shows astigmatism, (c) shows distortion, and (d) shows coma. The broken line in the spherical aberration diagram indicates the sine condition, the solid line in the non-aberration diagram indicates the sagittal, and the broken line indicates the meridional. “G” and “d” represent g-line and d-line, respectively.

  Numerical values indicating the optical characteristics of Example 1 are shown in Table 1. In Example 1, the focal length f, F number, and half angle of view ω of the entire optical system are f = 4.63 to 14.95, F number = 1.85 to 2.87, and ω = 47 by zooming, respectively. It varies in the range of .73 to 18.84.

  A variable A in Table 1 indicates a variable interval between the first lens group G1 and the second lens group G2. Variable B indicates a variable interval between the second lens group G2 and the aperture stop S. A variable C indicates a variable interval between the aperture stop S and the third lens group G3. Further, the variable D indicates a variable interval between the third lens group G3 and the fourth lens group G4. Variable E indicates a variable distance between the fourth lens group G4 and the transparent parallel plate F. Each interval varies with zooming as shown in Table 2.

  An asterisk (*) in Table 1 represents an aspheric surface, and the numerical value of the aspheric coefficient is as shown in Table 3.

The numerical values related to the conditional expressions shown above are as shown in Table 4.

  5A and 5B are optical arrangement diagrams of the projection zoom lens according to the second embodiment. FIG. 5A is a lens group arrangement at the wide-angle end (short focal end), and FIG. 5B is a lens group arrangement at the intermediate focal length. (C) shows the lens group arrangement at the telephoto end (long focal end). As shown in FIG. 5, at the time of zooming from the wide-angle end to the telephoto end, each lens group of the zoom lens moves as indicated by an arrow.

  The zoom lens shown in FIG. 5 has a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power sequentially from the object side to the image plane side along the optical axis. And a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power.

The aperture stop S is disposed between the second lens group G2 and the third lens group G3. The symbol F indicates “transparent parallel plate”. The transparent parallel plate F exemplifies various filters such as an optical low-pass filter and an infrared cut filter (transparent parallel plate on the object side) and a cover glass (transparent parallel plate on the seal glass image side) of an image sensor such as a CCD sensor. It is.

  The first lens group G1 includes a single first lens L11.

  The second lens group G2 includes a first lens L21, a second lens L22, and a third lens L23. The first lens L21 of the second lens group G2 is a hybrid aspherical lens that becomes an aspherical lens by a resin film provided on the object side surface.

  The third lens group G3 includes a first lens L31, a second lens L32, a third lens L33, a fourth lens L34, a fifth lens L35, and a sixth lens L36.

  The fourth lens group G4 includes a single first lens L41.

  The first lens group G1 to the fourth lens group G4 are each supported by a common support frame or the like appropriate for each lens group, and operate relatively for each lens group during zooming or the like. The aperture stop S moves independently of each lens group upon zooming from the short focal end to the long focal end.

  In the zoom lens according to Example 2, during zooming from the wide-angle end (short focal end) to the telephoto end (long focal end), the entire group of the first lens group G1 to the fourth lens group G4 moves. The first lens group G1 moves so as to be convex toward the image plane side, the second lens group G2 moves toward the image plane side, the third lens group G3 moves toward the object side, and the fourth lens group G4 moves. To do. By the movement of each lens group, the distance between the first lens group G1 and the second lens group G2 is increased, and the distance between the second lens group G2 and the third lens group G3 is decreased.

  6 to 8 are aberration diagrams of the zoom lens according to Example 2. FIG. 6 is an aberration curve diagram at the short focal end, FIG. 7 is an aberration curve diagram at the intermediate focal length, FIG. 8 is an aberration curve diagram at the long focal end, and (a) in each figure shows spherical aberration, ) Shows astigmatism, (c) shows distortion, and (d) shows coma. The broken line in the spherical aberration diagram indicates the sine condition, the solid line in the non-aberration diagram indicates the sagittal, and the broken line indicates the meridional. “G” and “d” represent g-line and d-line, respectively.

  Next, Table 5 shows numerical values indicating the optical characteristics of Example 2. In Example 2, the focal length f, the F number, and the half angle of view ω of the entire optical system are f = 4.63 to 14.95, F number = 1.85 to 2.77, and ω = 47 by zooming, respectively. The range is from 61 to 18.86.

  A variable A in Table 5 indicates a variable interval between the first lens group G1 and the second lens group G2. Variable B indicates a variable interval between the second lens group G2 and the aperture stop S. A variable C indicates a variable interval between the aperture stop S and the third lens group G3. Further, the variable D indicates a variable interval between the third lens group G3 and the fourth lens group G4. Variable E indicates a variable distance between the fourth lens group G4 and the transparent parallel plate F. As shown in Table 6, each interval changes with zooming.

  Further, the asterisk (*) in Table 1 represents an aspheric surface, and the numerical values of the aspheric coefficients are as shown in Table 7.

Further, numerical values relating to the conditional expressions shown above are as shown in Table 8.

  Here, correction of distortion occurring in the zoom lens according to Example 2 will be described. FIG. 17 is a diagram for explaining electronic correction of distortion in the zoom lens according to the second embodiment. In the zoom lens according to Example 2, the occurrence of distortion is suppressed near the intermediate focal length state and at the long focal end, but barrel distortion occurs at the short focal end.

  Therefore, as shown in FIG. 17, when imaging is performed at the short focal point of the zoom lens of Example 2, in order to electrically correct distortion, the effective imaging range 100 of the rectangular light receiving element 13 is The effective imaging range is set like a barrel-shaped imaging range 101. In the vicinity of the intermediate focal length state and the long focal end, the effective imaging range 100 is left as it is. Then, the image captured in the imaging range 101 at the short focal end is subjected to image conversion by image processing, and converted into rectangular image information with reduced distortion. As described above, in order to electrically correct the distortion, the image height at the short focal end is 4.55 mm, and the image height at the intermediate focal length and the long focal end is 4.9 mm.

  FIG. 9 shows an optical arrangement of the zoom lens according to Example 3, where (a) shows the lens group arrangement at the wide-angle end (short focal end), and (b) shows the lens group arrangement at the intermediate focal length. (C) shows the lens group arrangement at the telephoto end (long focal end). As shown in FIG. 9, at the time of zooming from the wide-angle end to the telephoto end, each lens group of the zoom lens moves as indicated by an arrow.

  The zoom lens shown in FIG. 9 includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power sequentially from the object side to the image plane side along the optical axis. And a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power.

The aperture stop S is disposed between the second lens group G2 and the third lens group G3. The symbol F indicates “transparent parallel plate”. The transparent parallel plate F exemplifies various filters such as an optical low-pass filter and an infrared cut filter (transparent parallel plate on the object side) and a cover glass (transparent parallel plate on the seal glass image side) of an image sensor such as a CCD sensor. It is.

  The first lens group G1 includes one first lens L11.

  The second lens group G2 includes a first lens L21, a second lens L22, and a third lens L23. The first lens L21 of the second lens group G2 is a hybrid aspherical lens that becomes an aspherical lens by a resin film provided on the object side surface.

  The third lens group G3 includes a first lens L31, a second lens L32, a third lens L33, a fourth lens L34, a fifth lens L35, and a sixth lens L36.

  The fourth lens group G4 includes one first lens L41.

  The first lens group G1 to the fourth lens group G4 are each supported by a common support frame or the like appropriate for each lens group, and operate relatively for each lens group during zooming or the like. The aperture stop S moves independently of each lens group upon zooming from the short focal end to the long focal end.

  In the zoom lens according to Example 3, during zooming from the wide-angle end (short focal end) to the telephoto end (long focal end), the entire group of the first lens group G1 to the fourth lens group G4 moves. The first lens group G1 moves so as to be convex toward the image plane side, the second lens group G2 moves toward the image plane side, the third lens group G3 moves toward the object side, and the fourth lens group G4 moves. To do. By the movement of each lens group, the distance between the first lens group G1 and the second lens group G2 is increased, and the distance between the second lens group G2 and the third lens group G3 is decreased.

  10 to 12 show aberration diagrams of the zoom lens according to Example 3. FIG. 10 is an aberration curve diagram at the short focal end, FIG. 11 is an aberration curve diagram at the intermediate focal length, FIG. 12 is an aberration curve diagram at the long focal end, and (a) of each figure shows spherical aberration, ) Shows astigmatism, (c) shows distortion, and (d) shows coma. The broken line in the spherical aberration diagram indicates the sine condition, the solid line in the non-aberration diagram indicates the sagittal, and the broken line indicates the meridional. “G” and “d” represent g-line and d-line, respectively.

  Next, Table 9 shows numerical values indicating the optical characteristics of Example 3. In Example 3, the focal length f, F number, and half angle of view ω of the entire optical system are f = 4.63 to 14.93, F number = 1.85 to 2.88, and ω = 47 by zooming, respectively. It varies in the range of 69 to 18.78.

  A variable A in Table 9 indicates a variable interval between the first lens group G1 and the second lens group G2. Variable B indicates a variable interval between the second lens group G2 and the aperture stop S. A variable C indicates a variable interval between the aperture stop S and the third lens group G3. Further, the variable D indicates a variable interval between the third lens group G3 and the fourth lens group G4. Variable E indicates a variable distance between the fourth lens group G4 and the transparent parallel plate F. As shown in Table 10, each interval changes with zooming.

  Further, an asterisk (*) in Table 9 represents an aspheric surface, and the numerical values of the aspheric coefficients are as shown in Table 11.

The numerical values related to the conditional expressions shown above are as shown in Table 12.

  FIG. 13 shows an optical arrangement diagram of the zoom lens according to Example 4, wherein (a) shows the lens group arrangement at the wide-angle end (short focal end), (b) shows the lens group arrangement at the intermediate focal length, (C) shows the lens group arrangement at the telephoto end (long focal end). As shown in FIG. 13, during zooming from the wide-angle end to the telephoto end, each lens group of the zoom lens moves as indicated by an arrow.

  The zoom lens shown in FIG. 13 includes a first lens group G1 having a positive refractive power and a second lens group G2 having a negative refractive power in order from the object side to the image plane side along the optical axis. And a third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power.

The aperture stop S is disposed between the second lens group G2 and the third lens group G3. The symbol F indicates “transparent parallel plate”. The transparent parallel plate F exemplifies various filters such as an optical low-pass filter and an infrared cut filter (transparent parallel plate on the object side) and a cover glass (transparent parallel plate on the seal glass image side) of an image sensor such as a CCD sensor. It is.

  The first lens group G1 includes one first lens L11.

  The second lens group G2 includes a first lens L21, a second lens L22, and a third lens L23. The first lens L21 of the second lens group G2 is a hybrid aspherical lens that becomes an aspherical lens by a resin film provided on the object side surface.

  The third lens group G3 includes a first lens L31, a second lens L32, a third lens L33, a fourth lens L34, a fifth lens L35, and a sixth lens L36.

  The fourth lens group G4 includes one first lens L41.

  The first lens group G1 to the fourth lens group G4 are each supported by a common support frame or the like appropriate for each lens group, and operate relatively for each lens group during zooming or the like. The aperture stop S moves independently from each lens group upon zooming from the short focal end to the long focal end.

  In the zoom lens according to Example 4, during zooming from the wide-angle end (short focal end) to the telephoto end (long focal end), the entire group of the first lens group G1 to the fourth lens group G4 moves. The first lens group G1 moves so as to be convex toward the image plane side, the second lens group G2 moves toward the image plane side, the third lens group G3 moves toward the object side, and the fourth lens group G4 moves. To do. By the movement of each lens group, the distance between the first lens group G1 and the second lens group G2 is increased, and the distance between the second lens group G2 and the third lens group G3 is decreased.

  FIGS. 14 to 16 show aberration diagrams of the zoom lens according to Example 4. FIGS. FIG. 14 is an aberration curve diagram at the short focal end, FIG. 15 is an aberration curve diagram at the intermediate focal length, FIG. 16 is an aberration curve diagram at the long focal end, and (a) in each figure shows spherical aberration, ) Shows astigmatism, (c) shows distortion, and (d) shows coma. The broken line in the spherical aberration diagram indicates the sine condition, the solid line in the non-aberration diagram indicates the sagittal, and the broken line indicates the meridional. “G” and “d” represent g-line and d-line, respectively.

  Next, Table 13 shows numerical values indicating the optical characteristics of Example 4. In Example 4, the focal length f, F number, and half angle of view ω of the entire optical system are f = 4.63 to 14.94, F number = 1.86 to 2.89, and ω = by zooming, respectively. It varies in the range of 47.85 to 18.37.

  A variable A in Table 13 indicates a variable interval between the first lens group G1 and the second lens group G2. Variable B indicates a variable interval between the second lens group G2 and the aperture stop S. A variable C indicates a variable interval between the aperture stop S and the third lens group G3. Further, the variable D indicates a variable interval between the third lens group G3 and the fourth lens group G4. Variable E indicates a variable distance between the fourth lens group G4 and the transparent parallel plate F. As shown in Table 14, each interval changes with zooming.

  An asterisk (*) in Table 13 represents an aspheric surface, and the numerical value of the aspheric coefficient is as shown in Table 15.

The numerical values related to the conditional expressions shown above are as shown in Table 16.

  As described above, in the zoom lens according to the present invention, the aberration is corrected at a high level in the specific configurations shown in Examples 1 to 4, and spherical aberration, astigmatism, field curvature, and lateral chromatic aberration are corrected. Also, distortion is sufficiently corrected. That is, it is apparent from each example that good optical performance can be secured.

  Next, an embodiment of a camera according to the present invention that uses the zoom lens according to Examples 1 to 4 in an imaging optical system and a portable information terminal as a camera will be described.

  FIG. 18A is a perspective view schematically showing the external appearance of a digital camera viewed from the object side, that is, the front side that is the subject side. FIG. 18B is a perspective view schematically showing the external appearance of the digital camera viewed from the back side, which is the photographer side. FIG. 19 is a block diagram schematically illustrating a functional configuration of the digital camera. Here, the camera is described taking a digital camera as an example, but the zoom lens according to the present invention may be employed in a silver salt film camera using a silver salt film as a conventional image recording medium. In addition, a personal information terminal device such as a so-called PDA (personal data assistant) or a cellular phone in which a camera function is incorporated is widely used. Such a portable information terminal device also includes substantially the same functions and configurations as a digital camera, although the appearance is slightly different. Therefore, you may employ | adopt the zoom lens which concerns on this invention as an imaging optical system of such a portable information terminal information device.

  As shown in FIG. 18, the digital camera includes a photographing lens 1, an optical viewfinder 2, a strobe 3, a shutter button 4, a camera body 5, a power switch 6, a liquid crystal monitor 7, an operation button 8, a memory card slot 9, and a zoom switch 10. Etc.

  Further, as shown in FIG. 19, the digital camera includes a central processing unit 11, an image processing device 12, a light receiving element 13, a signal processing device 14, a semiconductor memory 15 and a communication card 16. The digital camera includes a photographing lens 1 as an imaging optical system, a light receiving element 13 configured as an image sensor using a CMOS (complementary metal oxide semiconductor) imaging element or a CCD (charge coupled device) imaging element, have.

  An optical image of a subject (object) formed by the taking lens 1 is read by the light receiving element 13. As the photographing lens 1, the zoom lens according to the present invention described in the first to fourth embodiments is used. The output of the light receiving element 13 is processed by a signal processing device 14 controlled by the central processing unit 11 and converted into digital image information. That is, such a digital camera includes means for converting a captured image (subject image) into digital image information, which substantially controls the light receiving element 13, the signal processing device 14, and these. The central processing unit 11 is configured.

  The image information digitized by the signal processing device 14 is subjected to predetermined image processing in the image processing device 12 controlled by the central processing unit 11. After this image processing, it is recorded in the semiconductor memory 15 such as a nonvolatile memory. The semiconductor memory 15 may be a memory card loaded in the memory card slot 9 or may be a semiconductor memory incorporated (onboard) in the camera body.

  The liquid crystal monitor 7 can also display an image being shot. Also, an image recorded in the semiconductor memory 15 can be displayed. The image recorded in the semiconductor memory 15 can also be transmitted to the outside via a communication card 16 or the like loaded in a communication card slot (not shown).

  When the camera is carried, the objective surface of the photographing lens 1 is covered with a lens barrier (not shown). When the user operates the power switch 6 to turn on the power, the lens barrier opens and the objective surface is Exposed. At this time, inside the lens barrel of the photographing lens 1, the optical system of each lens group constituting the zoom lens is, for example, arranged at the wide angle end (short focal end). Thereafter, the arrangement of the optical system of each lens group is changed by operating the zoom switch 10, and the zooming operation is performed to the telephoto end (long focal end) through the intermediate focal length. Note that it is desirable that the optical system of the optical viewfinder 2 is also scaled in conjunction with the change in the angle of view of the photographing lens 1.

  Focusing is performed by the user pressing the shutter button 4 halfway. Focusing in the zoom lens according to the present invention includes movement of a part of a plurality of optical systems (for example, the second lens group G2 and the third lens group G3) constituting the zoom lens, movement of the light receiving element 13, and the like. Can be done by. When the shutter button 4 is further pushed down to the fully depressed state, photographing is performed, and then the processing as described above is performed. In order to display the image recorded in the semiconductor memory 15 on the liquid crystal monitor 7 and transmit it to the outside via the communication card 16 or the like, a predetermined operation may be performed using the operation button 8. The semiconductor memory 15 and the communication card 16 are used by being loaded into dedicated or general-purpose slots such as the memory card slot 9 and the communication card slot.

  The zoom lenses according to the first to fourth embodiments described above can be used in the above-described digital camera (imaging device) or portable information terminal device. As a result, the half angle of view at the wide angle end is a sufficiently wide angle of 45 degrees or more, the F number at the short focus end is 2.0 or less, and the F number at the long focus end is about 3.0. A zoom lens that can be made simple can be used as the photographing lens 1. Therefore, a small digital camera (imaging device) or a mobile phone having a zooming range that can sufficiently cover a normal shooting area with high image quality using a light receiving element having 10 to 20 million pixels or more. An information terminal device can be realized.

DESCRIPTION OF SYMBOLS 1 Shooting lens 2 Optical viewfinder 3 Strobe 4 Shutter button 5 Camera body 6 Power switch 7 LCD monitor 8 Operation button 9 Memory card slot 10 Zoom switch

JP 2000-347102 A JP 2001-188354 A JP2011-128361A

Claims (10)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. Thus, upon zooming from the short focal end to the long focal end, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens group In the zoom lens in which the interval of the fourth lens group changes,
An aperture stop is disposed between the second lens group and the third lens group,
The third lens group includes a positive lens L31, a positive lens L32, a negative lens L33, a negative lens L34, a positive lens L35, and a positive lens L36 in order from the object side.
The fourth lens group is composed of one or two lenses,
Focusing is performed with the fourth lens group,
The axial distance D34_T between the third lens group and the fourth lens group at the long focal point, and the focal length f4 of the fourth lens group are as follows:
Condition (1): 0.2 <D34_T / f4 <0.5
A zoom lens characterized by satisfying   The axial distance D34_W between the third lens group and the fourth lens group at the short focal point and the focal length f4 of the fourth lens group satisfy the condition (2): 0.05 <D34_W / f4 <0.15. The zoom lens according to claim 1.   The zoom lens according to claim 1 or 2, wherein the focal length f4 of the fourth lens group and the focal length fw of the short focal end satisfy the condition (3): 5 <f4 / fw <8.   The thickness D3 on the optical axis of the third lens group and the focal length fw of the short focal point satisfy the condition (4): 2 <D3 / fw <3. Zoom lens. The focal length f3 of the third lens group and the focal length fw of the short focal end are
Condition (5): 2.5 <f3 / fw <3.5
The zoom lens according to claim 1, wherein: The distance Da on the optical axis from the object side surface of the positive lens L31 to the image side surface of the negative lens L33 and the thickness D3 on the optical axis of the third lens group are as follows: Condition (6): 0.4 <Da / D3 <0.6
The zoom lens according to claim 1, wherein:   The zoom lens according to any one of claims 1 to 6, wherein the aperture stop moves independently of the lens groups upon zooming from the short focal end to the long focal end.   The distance TLs3_w between the stop and the third lens group at the short focal end and the distance TL2s_w between the second lens group and the stop at the short focus end satisfy the condition (7): 0.15 <TLs3_w / TL2s_w <0.40. Item 8. The zoom lens according to Item 7.   A camera comprising the zoom lens according to claim 1 as a photographing optical system.   A portable information terminal device comprising the zoom lens according to claim 1 as a photographing optical system of a camera function unit.

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